The production of areas of partial shrinkage and undulation on textile fabrics containing synthetic fibres by the local application of organic agents causing the synthetic fibres to swell and by the ensuing shrinkage of the synthetic fibres by thermal action is well-known, versions of which are sometimes referred to as "Plisse printing." For instance, a method has been proposed whereby areas of partial shrinkage are produced on fabrics of polyester fibres by the application of printing pastes containing phenol and ensuing thermal treatment at approximately 120.degree. C., during which the printed areas are caused to shrink, thereby imparting an undulating effect to the unprinted areas.
A further method is known to the trade whereby woven or knitted fabrics containing at least a proportion of polyamide fibres are first printed with a resist paste to the specification of the pattern and treated with a solution of swelling agents, such as formic, acetic or halogenated acetic acid, following which they are removed by washing with water and dried. The areas containing the resist paste show an insulating effect, whereas the other areas remain totally flat.
These known processes have a number of shortcomings, one being that the areas treated with the swelling agent frequently show signs of stiffness and hardness; the other, that synthetic fibres treated with swelling agents invariably behave like undrawn fibres owing to their high degree of swelling and exhibit increased stretching particularly apparent when the garment manufactured from these fibres is laundered or worn.
A further handicap, of a more serious nature, is that the swelling agents applied diffuse only very slowly into the liquor in the ensuing washing operation to which the woven and knitted fabrics are subjected, some always remaining in the fibre for all practical purposes, thereby easily causing dermatological problems. Moreover, as many of the swelling agents applied are sensitive to light, the woven or knitted fabrics treated practically always show signs of yellowing, which are more or less pronounced. Finally, the vaporization or sublimation of the swelling agents applied represent a hazard during the drying operation and should not be discounted from an ecological viewpoint.
The object of the invention is to remove the known shortcomings and to devise a simple, readily reproducible method of producing pronounced cloque or undulating effects of a permanent, uniform nature. This requirement is met in the invention by carrying out a first heat-treatment preferably in a calendering operation, for example, friction calendering with the surface temperatures of the rolls ranging between 100.degree. C. and 200.degree. C., for temporarily increasing the density of the threads in the fabric. The first heat-treatment may also be carried out with the fabric under tension, for example, on a stenter for a period of 30 to 60 seconds. Following this, the fabric is printed with a heat-resistant resist to the specifications of a pattern, followed by a second heat-treatment preferably carried out without tension for a period of 30 seconds to 10 minutes for decreasing the density of the threads in those areas not printed with the resist paste.
The effectiveness of the new process is remarkable because it would not be expected in the trade that the heat-treatment alone would produce pronounced shrinkage of a uniform nature in those areas of a fabric not printed with a resist paste. The principal advantage of the process invented is that it does not require the application of chemical agents that are hazardous from toxicological and ecological viewpoints or the use of specialized equipment. As opposed to coventional processes, the shrinkage effects that are achieved in the process invented are basically more resistant to modern care requirements; i.e., they show increased stability towards laundering and dry cleaning. Furthermore, they are able to withstand mechanical strain as long as the tensile strength of the untreated woven or knitted fabric is not exceeded. Suited as base materials for the process invented are fabrics woven or knitted from continuous-filament yarns, preferably textured yarns, or staple yarns. These are formed from synthetic fibres, such as polyester, polyamide, or polyacrylonitrile.
Printing pastes in the form of aqueous solutions are primarily suited to producing resists capable of withstanding high temperatures. Solutions in organic solvents, dispersions or emulsions may also be employed. The printing pastes consist of thickeners made from natural products, such as alginates, starches, especially those starches derived by retting, hydrolysis or chemical modification, for example. Furthermore, water-soluble cellulose or galactomannan derivatives may be employed. In addition, natural plant gums, such as tragacanth and gum arabic and, last but not least, 100% synthetic water-soluble high-grade polymers, such as polyvinyl alcohol and salts of polyacrylic acid, are suitable.
When the first heat-treatment consists of friction-calendering operations, the cloque or undulating effects may be combined with lustrous or mat effects. These effects may be produced on a white, dyed or printed fabric. The resist pastes may also be applied, with accurate registration, in conjunction with a color print, whether by conventional printing methods or discharge printing, whereby the areas showing the undulating effect also exhibit the ground color. Finally, the areas showing the undulating effect may also be dyed or discharge printed by adding colors and/or discharge agents to the resist paste.